R33 Rb30 Conversion

[shanef]

Shane, have a read above at my previous posts. You'll see I said its not the best comparison.

Regardless, twins offer better turbo response due to less inertia.

Providing there is sufficient exhaust gas smaller turbo's are able to go from idle rpm to 80,000rpm quicker than a wheel 2x its size.

Why would Nissan throw ceramic turbines on their turbo's? To lower inertia and provide better response from the turbo.

i did i did

But a turbo with double the hp ability doesn't have double the rotating dimensions, or double the rotating inertia

i'd tend to agree with that.

even with a big single, u can make them flow more hp by changing the rear housings, and when u do that u dont change the size or dimension of the wheels themselves.

i guess it's only going to be theories ubtil someone that's cashed up does some physical research into it.

[Cubes]

But a turbo with double the hp ability doesn't have double the rotating dimensions, or double the rotating inertia

But I'm not saying the big turbo has double the 'intertia lag'.

If your at an rpm where the turbo is receiving sufficient exhaust gas for quick full spool then that is where you are able see/measure the inertia 'lag' so to speak.

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Shane; Parallel twins are well known to provide better response over a similiar sized big single. So no theory.

A large turbo has more of this inertia lag; a smaller turbo has less. Providing they are both at an rpm where they are able to spool easily the smaller turbo's will spool/spin up quicker. Simple physics.

Think back to 89 with the first release of the GTR. Why would nissan bother with the added expense of a twin turbo system?

[GTRgeoff]

Inertia is a function of the radius to the 4th power, so a turbo with a radius of 20mm will have an inertial factor of 160000mm^4, while a turbo with a radius of 30mm will have a factor of 810000mm^4 or about 5.1 times as much resistance to acceleration. Now there will be some detailed integrations of the actual masses in the rotor construction and the material used but pound for pound a larger turbo is a diminishing return for response so you increase cubes to offset that.

Sorry guys but the engineering wins. Twins for response. Singles for lag monster drag and dyno queens.

[sh@un]

Isn't it to the cube?

When you rev an engine twice as hard, you exert 8 times as much force on the reciprocating components.

[VHR32]

There was a debate about GT35's in either .82 and 1.06 sizes and which ones are better for drivability/traction etc on the race track. Most people said the .82 ones came on too strong and caused wheel spin where as the 1.06 could be controlled with the throttle.

So how can twins which are far more reponsive, be better for traction?! I thought they would wheel spin too much.

Edited July 26, 2007 by VHR32

[Cubes]

The twin's 'shouldn't' be better for traction as having less rotational inertia means they come on harder in the lower gears.

But nothing wrong with that if you have 4 wheels clawing at the bitchumen.

[r33_racer]

joel not everyone drives/races a gtr....only blokes with no skill require four wheel drive. Real men drive gtst's!

the slight response difference between the twins or single isnt that big of a deal in most cases...maybe if your racing for sheep stations. In almost every circumstance you can offset it with something else that will make your car quicker around the track or on the street. As is the problem with most people is the cost involved in it all. Twin setups will always cost more then single.

VHR32 - ive raced with a .82 rear gt35r and i think a 1.06 rear would be better for control, but the lag side of things would outweigh the benefit of the control. I would rather then extra response from the .82 and control the power better with my foot, not only that but having a disadvantaged mechanical setup teaches you to be a better racer as it forces you to adapt rather then just relying on a more superior setup to improve your times/position.

[Scooby]

There was a debate about GT35's in either .82 and 1.06 sizes and which ones are better for drivability/traction etc on the race track. Most people said the .82 ones came on too strong and caused wheel spin where as the 1.06 could be controlled with the throttle.

So how can twins which are far more reponsive, be better for traction?! I thought they would wheel spin too much.

broadly a big single is just as responsive as twins in its ideal operating range. problem is singles have a narrower and sharper effective rpm operating range, and this can have some disadvantages. singles and twins will both respond well from boost threshold until they max out, in the case of the twins say between 3500 and 7500 rpm, the single between 5000 and 7500 rpm. twins are more responsive but the power production is not as on/off. the sudden power production of the single is what brings the big bang and the loss of traction.

[Cubes]

Michael, lol.. Can't agree with you more.

Have you checked out the aus circuit lap time thread created by Roy?

Get some of your rwd lap times in there.

http://www.skylinesaustralia.com/forums/in...showtopic=46199

[r33_racer]

ive seen it and put our old old times in there...but im so slack to update it all. One day ill get around to it.

[shanef]

joel not everyone drives/races a gtr....only blokes with no skill require four wheel drive. Real men drive gtst's!

the slight response difference between the twins or single isnt that big of a deal in most cases...maybe if your racing for sheep stations. In almost every circumstance you can offset it with something else that will make your car quicker around the track or on the street. As is the problem with most people is the cost involved in it all. Twin setups will always cost more then single.

VHR32 - ive raced with a .82 rear gt35r and i think a 1.06 rear would be better for control, but the lag side of things would outweigh the benefit of the control. I would rather then extra response from the .82 and control the power better with my foot, not only that but having a disadvantaged mechanical setup teaches you to be a better racer as it forces you to adapt rather then just relying on a more superior setup to improve your times/position.

awww look at the little jealous kid

[r33_racer]

ill show you jealous shane...your coming round tomorrow arvo for bbq yeh?

bring ya guns mate...its on like donkey kong!

[GTRgeoff]

Shane!! Mike!! Play nice or you will be fed vegetarian snags at the BBQ!!!!

Sorry guys I made an error.

I was locked onto a solution for mass moment of inertia which is a solution in mm^4.

Basic rotating inertia is a quadratic with a solution in mm^2 but regardless the difference in the above example is 400mm^2 and 900mm^2 or 2.25 times the rotating inertia. So even with double the exhaust gas a larger turbo by 10mm is still going to exhibit a measurable lag response. Add to that tolerances will have to be greater in a larger turbo to account for inertial growth and life cycle creep.

[RB120WHY]

What do you guys think of a RB25/30 with the GT35R and the small 0.63 ext ???

Too responsive for a sub 1000kg car ???

[shanef]

ill show you jealous shane...your coming round tomorrow arvo for bbq yeh?

bring ya guns mate...its on like donkey kong!

my guns roll with me

i'll be there with empty pockets, and i'll be leavin with full pockets :sorcerer:

Shane!! Mike!! Play nice or you will be fed vegetarian snags at the BBQ!!!!

Sorry guys I made an error.

I was locked onto a solution for mass moment of inertia which is a solution in mm^4.

Basic rotating inertia is a quadratic with a solution in mm^2 but regardless the difference in the above example is 400mm^2 and 900mm^2 or 2.25 times the rotating inertia. So even with double the exhaust gas a larger turbo by 10mm is still going to exhibit a measurable lag response. Add to that tolerances will have to be greater in a larger turbo to account for inertial growth and life cycle creep.

who the fark invited you?

theory is all well and good, but sometimes it just dont work in real life

EDIT:- Im not saying that theory above dont work lol

[Al]

What do you guys think of a RB25/30 with the GT35R and the small 0.63 ext ???

Too responsive for a sub 1000kg car ???

What's the point??? A GT35R (0.63) will produce similar results as a GT30R (0.82). I would personally go with the gt30r, with the 0.82 housing, as it would give a broader range of power. You may find that the 0.63 housing will choke the rb30, higher up in the rev range, causing the power to drop dramatically.

Even a GT35R (0.82) would be a great combo on a rb30det/t

[Al]

Speaking of which.........

Joel, any progress yet ?

[Cubes]

Al,

Your worse than my missus harassing me to get the car backtogether. lmao

Soon soon; I broke my plenum to inlet manifold gasket so nissan will have me one on Monday.

[Al]

Hahahahaha.............

Just impatient

Excited to see the potential of my combo, once complete.

[GTRgeoff]

theory is all well and good, but sometimes it just dont work in real life

EDIT:- Im not saying that theory above dont work lol

Then say nothing and appear wise grasshopper.

Usually only the uneducated cast doubt on the science and engineering, but hey, both are still booming industries.